1. Field of the Invention
This invention generally relates to improvements in lamps, especially ultraviolet lamps used in air and water purifiers.
2. Description of Related Art
Ultraviolet air and water or other liquid purifiers are known for disinfecting contaminated air or water or other liquid for domestic or commercial use. Such purifiers include at least one lamp for emitting ultraviolet radiation into a chamber filled with contaminated air or water or other liquid to kill microorganisms therein. In conventional manner, the lamp includes two electrodes spaced apart within an elongated arc tube containing a gas, particularly mercury vapor with or without additives. A pair of end caps are mounted at the ends of the tube. Each electrode contains two lead wires from the lamp seal each of which, or in some instances only one, are electrically connected to respective contact(s) or terminal pin(s). The lamp is typically inserted endwise into a sleeve installed in the water, other liquid or air purifier with or without the sleeve. To simplify insertion and electrical connection, the pins are conveniently mounted on one of the end caps. When the electrodes are energized by voltage from an electrical power supply, an electrical discharge is initiated in the gas between the electrodes. This discharge reacts with a layer of a radiation-emitting material coated on an interior surface of the arc tube and causes ultraviolet radiation to be emitted from the lamp in a manner well known in the art.
An example of an ultraviolet lamp of the type described above is disclosed in U.S. Pat. No. 5,166,527 ('527), all of the contents of which are incorporated herein by reference. The '527 patent discloses a lamp, especially useful as an ultraviolet lamp for use in a water purifier, comprising an elongated, hollow arc tube extending along a longitudinal axis between opposite end regions. The tube contains a gas, preferably mercury vapor with or without additives. A pair of electrodes is spaced apart along the longitudinal axis. The electrodes are respectively mounted within the arc tube at the end regions thereof. A pair of end caps is respectively mounted at the end regions of the arc tube. A first electrical contact or pair of electrical contacts or terminal pins extends in mutual parallelism along the longitudinal axis and is electrically connected to one or both of the electrode lead wires. A second electrical contact or pair of electrical contacts or terminal pins extends in mutual parallelism along the longitudinal axis and is electrically connected to one or both of the other of the electrode lead wires. Both pairs of pins are mounted on, and extend outwardly along the longitudinal axis of, one of the end caps. A wire conductor is, or two wire conductors are, located exteriorly of the tube and electrically connected to one pin or one pair of pins at one end region of the tube, as well as to the electrode at the other end region of the tube.
Two embodiments, of the lamp disclosed in the '527 patent are shown in prior art FIGS. 1 and 2. As shown in FIGS. 1 and 2, the pairs of pins are offset relative to each other along the longitudinal axis. This offset resists the formation of an electrical arc between the pairs of pins exteriorly of the arc tube, especially in the presence of the moisture-laden, humid environment of the water purifier.
Still referring to prior art FIGS. 1 and 2, the one end cap has a stepped outer end wall having a pair of wall portions lying in mutual parallelism in planes generally perpendicular to the longitudinal axis. The first pair of pins is supported on, and extends through, one of the end wall portions for a predetermined distance, and the second pair of pins is supported on, and extends through, the other of the end wall portions for the same predetermined distance. The planes of the end wall portions are spaced apart by a predetermined spacing larger than said predetermined distance in order to still further prevent electrical arcing between the pairs of pins exteriorly of the arc tube. A barrier wall internally of the one end cap physically separates the electrical connections to the two pairs of pins to resist the formation of an electrical arc between the pairs of pins interiorly of the one end cap. The barrier wall is advantageously made of the same non-conductive material as the one end cap.
In addition to the two-tiered stepped bases of the '527 patent, other multi-tiered bases have been manufactured including those bases shown in prior art FIGS. 3-7.
Although well-suited for their intended purposes, there continues to be a need for improved lamp base designs, particularly ultraviolet lamps.